Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2007
Publication Date: 12/2/2007
Citation: Whitaker, T.B., Slate, A., Greene, J., Hendrix, K., Sanders, T.H. 2007. Uncertainty associated with sampling peanuts to determine fruity-fermented off flavor. Peanut Science 34:126-134. Interpretive Summary: Peanuts cured at elevated temperatures will produce compound that have an objectionable off-flavor when consumers eat peanuts and peanut products. Both domestic and international peanut manufactures test raw peanuts for off-flavor before processing and reject lots that have off-flavor intensities above an established threshold. It is difficult to determine off-flavor intensity of large shipments because of the errors associated with sampling, sample preparation, and analysis, collectively called the off-flavor test procedure. Errors associated with the off-flavor test procedure results in some lots being misclassified. Some of the good lots test bad and some of the bad lots test good. The errors associated with measuring off-flavor in peanuts were determined. Once the magnitude of the testing errors are know, methods can be developed to reduce the testing errors, which will reduce the number of lots mis-classified. This will provide a better quality product to the consumer and reduce economic loss to processors and food manufacturers.
Technical Abstract: Individual peanut kernels may develop a fruity fermented (FF) off-flavor if exposed to elevated temperatures soon after digging. Typically, high moisture, immature peanuts exposed to temperatures above 35ºC either in the windrow or during artificial curing may develop the FF off-flavor. Because of the uncertainty associated with sampling and off-flavor measurement, it is difficult to obtain a precise estimate of the true FF intensity within a bulk lot. The objectives of this study were to determine the variability associated with the sampling and measurement steps of the test procedure used to measure FF flavor in a bulk lot and to describe the FF distribution among replicated sample test results taken from the same lot. Twenty test samples of 250 g each were randomly taken from 20 medium grade lots of runner-type peanuts identified by commercial testing as having FF off-flavor intensities ranging from 0.0 (no FF off flavor) to 4.0. Each test sample was prepared according to published guidelines and the FF intensity of each sample was measure by 8 members of a trained USDA descriptive sensory panel. The total variability associated with the FF test procedure was partitioned into sampling and measurement variances for each lot. Each variance was a function of the FF intensity in the lot. Using the standard commercial FF test procedure (300 g sample and averaging the score of 5 panel members), the measurement and sampling variances accounted for 20.5 % and 79.5 % of the total error, respectively. The FF distribution among replicated sample test results from each lot tended to be positively skewed and could be described by the compound gamma distribution over a wide range of lot FF intensities. The best use of resources to reduce the total variability of the FF test procedure would be to increase sample size to reduce variability of the sampling step.